表没食子儿茶素没食子酸酯的多巴胺能神经元保护作用

目的 研究绿茶多酚的主要单体成分表没食子儿茶素没食子酸酯（EGCG）的多巴胺能神经元保护作用。方法利用1-甲基-4-苯基-1，2，3，6-四羟吡啶（MPTP）及其代谢产物1-甲基-4-苯基吡啶（MPP＋）分别造成选择性多巴胺能神经元损伤动物模型和细胞模型．给予不同剂量EGCG，免疫组织化学染色方法标记酪氨酸羟化酶（TH）阳性细胞作为多巴胺能神经元标志，通过体视学方法观察不同剂量EGCG对阳性细胞数目的影响，同时利用膜抗原CD11b标记小胶质细胞，观察EGCG对小胶质细胞激活的作用。结果在MPP＋诱导的原代培养中脑腹侧多巴胺能神经元损伤模型中，预先给予EGCG1μmol／L-100μmol／L可显著减轻MPP＋诱导的多巴胺能神经元减少，保护率为22．2％～80．5％。在体情况下，1mg／kg剂量EGCG腹腔注射对MPTP模型小鼠A9区TH免疫阳性细胞丢失的保护率为71．7％．对中脑区域总TH免疫阳性细胞数丢失的保护率为50．9％，5mg／kg和10mg／kg剂量组中脑各区域TH阳性神经元数量均较模型组高（P〈0．05），同时，EGCG对MPTP所致的中脑部位小胶质细胞的激活具有抑制效应。结论本研究结果提示EGCG在一定剂量范围内对多巴胺能神经元具有显著的保护作用，具有潜在治疗帕金森病的价值，EGCG对多巴胺能神经元的在体保护作用可能与其抑制小胶质细胞的激活密切相关。

Epigallocatechin gallate protects dopaminergic neurons against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity by inhibiting microglial cell activation

OBJECTIVE: To observe whether the dopaminergic neuroprotective effect of (-)-epigallocatechin gallate (EGCG) is associated with its inhibition of microglial cell activation in vivo. METHODS: The effects of EGCG at different doses on dopaminergic neuronal survival were tested in a methyl-4-phenyl-pyridinium (MPP+)-induced dopaminergic neuronal injury model in the primary mesencephalic cell cultures. With unbiased stereological method, tyrosine hydroxylase-immunoreactive (TH-ir) cells were counted in the A8, A9 and A10 regions of the substantia nigra (SN) in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated C57BL/6 mice. The effect of EGCG on microglial activation in the SN was also investigated. RESULTS: Pretreatment with EGCG (1 to 100 micromol/L) significantly attenuated MPP+-induced TH-ir cell loss by 22.2% to 80.5% in the mesencephalic cell cultures. In MPTP-treated C57BL/6 mice, EGCG at a low concentration (1 mg/kg) provided significant protection against MPTP-induced TH-ir cell loss by 50.9% in the whole nigral area and by 71.7% in the A9 region. EGCG at 5 mg/kg showed more prominent protective effect than at 1 or 10 mg/kg. EGCG pretreatment significantly inhibited microglial activation and CD11b expression induced by MPTP. CONCLUSION: EGCG exerts potent dopaminergic neuroprotective activity by means of microglial inhibition, which shed light on the potential use of EGCG in treatment of Parkinson's disease.